In service station environments, fuel is delivered to fuel dispensers from underground storage tanks (UST), sometimes referred to as fuel storage tanks. USTs are large containers located beneath the ground that contain fuel. A separate UST is provided for each fuel type, such as low octane gasoline, high octane gasoline, and diesel fuel. In order to deliver the fuel from the USTs to the fuel dispensers, a submersible turbine pump (STP) is provided that pumps the fuel out of the UST and delivers the fuel through a main fuel piping conduit that runs beneath the ground in the service station.
Due to regulatory requirements governing service stations, the main fuel piping conduit is usually required to be double-walled piping. Double-walled piping contains an inner piping that carries the fuel. An outer piping forming an outer annular space, also called an “interstitial space,” surrounds the inner piping so as to capture and contain any leaks that occur in the inner piping, so that such leaks do not reach the ground. An example of double-walled fuel pipe is disclosed in U.S. Pat. No. 5,527,130, incorporated herein by reference in its entirety.
It is possible that the outer annular space of the double-walled fuel piping could fail, thereby leaking fuel outside of the fuel piping if the inner piping were to fail as well. Fuel sump sensors that detect leaks are located underneath the ground in the STP sump and the fuel dispenser sumps. These sensors detect any leaks that occur in the fuel piping at the location of the sensors. However, if a leak occurs in the double-walled fuel piping between these sensors, it is possible that a leak in the double-walled fuel piping will go undetected since the leaked fuel will leak into the ground, never reaching one of the fuel leak sensors. The STP will continue to operate as normal, drawing fuel from the UST; however, the fuel may leak to the ground instead of being delivered to the fuel dispensers.
Double-walled fuel piping is located outside of the fuel dispenser beneath the ground in conduits that deliver fuel from the STP to the fuel dispensers. However, once the fuel supply piping enters into the fuel dispenser, the fuel supply piping that is fed to the hydraulic components in the fuel dispenser is not double-walled piping. This internal fuel supply piping inside the fuel dispenser is still capable of incurring a breach thereby leaking fuel to the environment. A fuel dispenser does not contain a sump inside the fuel dispenser to collect leaked fuel and therefore a liquid sensor is not employed to detect leaked fuel. If a breach occurs in the fuel supply piping inside the fuel dispenser, such leak will go undetected since there are no mechanisms to detect or contain such leak.
The aforementioned patent application Ser. No. 10/703,156 and its predecessors discuss leak prevention systems whereby the interstitial space in the double-walled piping is monitored and breaches are detected. The interstitial space is pressure monitored to determine if a breach exists in the outer piping of the double-walled piping. In this manner, a breach in the outer wall is detected regardless of whether a leak has occurred in the inner piping so that an alarm and/or preventive measures can be taken to prevent the leaking of fuel collected in the interstitial space should a breach occur in the inner piping.
Recent proposed changes in state and federal regulations will tighten the requirements to contain leaks and will further require better leak detection so that environmental damage may be minimized. As a result, it is becoming imperative that all potential leak sources be evaluated and steps taken to detect and contain leaks in the piping systems. One area that has not been specifically addressed by the parent disclosures and the prior art is leak prevention of fuel supply piping located inside the fuel dispenser.